Its Openreach not BT Retail that you need to contact, however I believe they only pass them on to third party companies for disposal or re-use.
Direct links are not allowed on this forum, but here is a screenshot of one website, but you may find more on a Google search.
My 11 year old daughter (along with our parish councillor) is seeking help from BT to help rehome local wildlife from our village church which is due to be demolished. She is asking BT if they have one or two old unused telegraph poles that could be erected so that owl boxes could be attached to them. Where should she send her letter seeking assistance? Many thanks. Michelle